ACK: [bionic:linux-azure-4.15, focal:linux-azure] LP:#1913294 - Sync FSGSBASE patches in azure kernel with mainline

[Stefan Bader]

On 26.01.21 14:17, Marcelo Henrique Cerri wrote:
> BugLink: https://bugs.launchpad.net/bugs/1913294
> 
> Some of the patches are already applied. For 5.8 specifically, not
> change is necessary because we dropped our sauce patches when
> preparing groovy:linux-azure and picked all the changes from upstream
> up to 5.9.
> 
> For 5.4 (focal:linux-azure) the changes are clean cherry-picks. For
> 4.15 (bionic:linux-azure-4.15) one additional change that was
> introduced in 4.17 was necessary and one patch had to backport just to
> adjust context.
> 
> Testing was performed by Microsoft that confirmed the changes are ok.
> 
> As bug description:
> 
> [Impact]
> 
> To include the missing upstream patches to the 4.15 and 5.4 kernel.
> 
> * x86/entry/64: Do not use RDPID in paranoid entry to accommodate KVM:
> - occasional random failure when running KVM
> * x86/fsgsbase/64: Fix NULL deref in 86_fsgsbase_read_task
> - Google folks found this when running their fuzzy test cases. Don't know how realistic this can hit.
> * x86/fsgsbase: Fix Xen PV support
> * x86/process/64: Make save_fsgs_for_kvm() ready for FSGSBASE
> - these two are for VMMs.
> 
> Some of these are already included in our azure kernels. 5.8 doesn't
> need them because we already synced with upstream while preparing it.
> 
> [Test Case]
> 
> Since we are syncing with mainline a boot test and a regression test
> in ACC instances should be enough to confirm the changes are working.
> 
> Since these instances are not publicly available yet, Msft is helping
> us to test this changes.
> 
> [Where problems could occur]
> 
> This affects the SGX driver that is only available on ACC instances
> (which is not widely used yet).
> 
> ---
> Sean Christopherson (1):
>   x86/entry/64: Do not use RDPID in paranoid entry to accomodate KVM
> 
> Thomas Gleixner (1):
>   x86/process/64: Make save_fsgs_for_kvm() ready for FSGSBASE
> 
>  arch/x86/entry/calling.h         | 10 ++++++----
>  arch/x86/include/asm/processor.h |  4 +---
>  arch/x86/kernel/process_64.c     | 15 +++++++++------
>  arch/x86/kvm/vmx/vmx.c           |  2 +-
>  4 files changed, 17 insertions(+), 14 deletions(-)
> 

Testing ok, specific kernels and changes look comparable.

Acked-by: Stefan Bader <stefan.bader at canonical.com>

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